1. Field of the Invention
This invention relates to resist materials for forming fine resist patterns by means of a high energy beam such as an electron beam, X-rays or the like and the process for forming patterns of such resist in the production of semiconductors, magnetic bubble elements, optical applied parts and the like.
2. Description of the Prior Art
Recently there have been remarkably severe demands for high integration of semiconductor devices. In connection with such demands, it is particularly required for fine work in such process, that resist patterns are formed by means of an electron beam (EB) or the like, and they are precisely transferred to a substrate in accordance with dry etching wherein ions, plasma or the like is utilized.
In this respect, as a matter of course, high resolution as well as high resistance to dry etching are required for the resist materials utilized for such fine work as described above. However, for example, heretofore well-known radiation sensitive resists will not necessarily satisfy the above described requirements. For instance, polymethyl methacrylate (hereinafter referred to simply as "PMMA") which has been known as a high resolution positive type EB resist has in sufficient dry etching resistance. Methacrylic polymers, polybutene-1-sulfone and the like which have been utilized as the other positive type resists have lower resolving power than that of PMMA and dry etching resistance equivalent to or lower than that of PMMA, so that such characteristic properties are also insufficient.
On the other hand, acrylic resists such as polyglycidyl methacrylate and the like, among negative type resists are insufficient in resistance to dry etching, as in the case of the aforesaid PMMA. Furthermore, for example, polystyrene or chloromethylated polystyrene obtained by imparting a sensitive group to polystyrene contains phenyl group(s) so that such chloromethylated polystyrene is excellent in the aforementioned dry etching resistance. On the other hand, however, these resists are crosslinking type resists so that there are disadvantages such that occurrence of scum and bridging due to swelling of the pattern cannot be avoided and like defects. Thus, it is impossible, in fact, to form a resist pattern with 0.2 .mu.m features.
Moreover a method wherein the molecular weight of resist materials is decreased for forming fine patterns has been known in general. However, this method has a disadvantage such that the sensitivity of the resulting resist materials decreases significantly. Particularly, there is a disadvantage in that an oligomer having a molecular weight of 1,000 or less exhibits very low sensitivity so that such oligomer cannot be put to practical use.
As described above, there is strong demand in respect of resist materials having high resolving power as well as excellent dry etching resistance as described hereinbefore at present. Under these circumstances, early establishment of a process for forming fine patterns by means of such resists as mentioned above is expected.